For many uses of fibrous synthetic polymers, it is desirable to minimize the weight of fiber needed to spread over an area. This qualitative property of a fiber is known as "cover". Another quality of fibers for certain end uses (like for carpet yarn) is the fiber's ability to hide soil. Yet, while for some end uses it is important to obtain high cover and good soil hiding, sparkle and/or luster should not be sacrificed. For example, carpet yarns should provide the greatest cover and hide soil well, yet remain lustrous. Efforts to achieve a fabric having these characteristics have largely failed since fiber properties leading to soil hiding tend to lessen luster. Presently, Applicants are unaware of any fiber which effectively achieves all these qualities.
Trilobal fibers are known to provide cover superior to round cross-sections and it is known to make trilobal and pseudo-trilobal filaments (e.g., deltas, T-shapes). Exemplary are U.S. Pat. No. 3,981,948 to Phillips, U.S. Pat. No. 3,194,002 to Raynolds et at., U.S. Pat. No. 2,939,201 to Holland, U.S. Pat. No. 4,492,731 to Bankar et al. and Japanese Kokai 42-22574.
It is also known to provide voids in filaments and that many times these voids result in improved soiling hiding performance. U.S. Pat. No. 3,745,061 to Champaneria et al. and U.S. Pat. No. 4,407,889 to Gintis et al. show non-round filaments having one or more voids.
It is known also to provide trilobal or pseudo-trilobal fibers which have one or more voids. Exemplary are U.S. Pat. No. 3,095,258 to Scott, U.S. Pat. No. 3,357,048 to Cobb, Jr., U.S. Pat. No. 3,493,459 to McIntosh et al., U.S. Pat. No. 3,558,420 to Opfell, U.S. Pat. No. 4,279,053 to Payne et al., U.S. Pat. No. 4,364,996 to Sugiyama, U.S. Pat. No. 4,956,237 to Samuelsom and British Patent No. 843,179 to Siemer et al.
U.S. Pat. No. 4,648,830 to Peterson et al. discloses a spinneret for manufacturing hollow trilobal cross-section filaments. The filaments disclosed therein have one axially extending hole in each lobe.